1. Field of the Invention
Exemplary aspects of the present invention relate to a development device and an image forming apparatus, and more particularly, to a development device and an image forming apparatus for forming a high quality image without uneven image density.
2. Description of the Related Art
A related-art image forming apparatus, such as a copier, a facsimile machine, a printer, a plotter, or a multifunction printer having at least one of copying, printing, scanning, plotter, and facsimile functions, forms a toner image on a recording medium (e.g., a sheet) according to image data by electrophotography. For example, a charging device charges a surface of a latent image carrier. An optical writer emits a light beam onto the charged surface of the latent image carrier to form an electrostatic latent image on the latent image carrier according to the image data. A development device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the latent image carrier. The toner image is transferred from the latent image carrier onto a sheet. A fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image on the sheet. Thus, the toner image is formed on the sheet.
Recently, in order to satisfy an increasing demand for full color image formation, an image forming apparatus may include a plurality of development devices to form toner images in colors different from each other. The toner images are superimposed on a latent image carrier to form a color toner image thereon.
One example of a related-art image forming apparatus includes development devices using a toner cloud development method. The development devices do not contact a latent image carrier and form a toner cloud between the latent image carrier and development rollers included in the development devices due to an effect of an alternating current electrical field generated by an alternating current voltage source. Toner particles in the toner cloud may be attracted to a latent image formed on the latent image carrier and used for development of the latent image. For example, while the latent image carrier bearing the latent image rotates, the development devices adhere toner particles in different colors, respectively, to the latent image on the latent image carrier. In other words, a toner image in one color may be superimposed on another toner image in a different color, thereby forming a full color toner image.
Another example of a related-art image forming apparatus includes a development device using an effect of an electrical field curtain. Such development device also does not contact a latent image carrier and forms the electrical field curtain between the latent image carrier and a development roller included in the development device by application of an alternating current voltage to electrodes. The electrical field curtain may convey toner particles to the latent image carrier so as to form a toner image thereon.
However, due to the alternating current electrical field formed between the latent image carrier and the development device, some toner particles may be removed from the toner image formed on the latent image carrier and return to an inside of the development device, resulting in a faulty image. In addition, the toner particles may be mixed with another toner particles in a different color.
Therefore, in order to form a high-quality full color toner image, there is a need for a technology to form a toner cloud without generating an alternating current electrical field between a latent image carrier and a development device.